Rotary anode cathode ray tube



' March 3, 1964 G. s. P. FREEMAN 3,123,733

ROTARY ANODE CATHODE RAY TUBE Filed Feb. 2 1961 Ff'c 2 United StatesPatent 3,123,733 ROTARY ANODE CATHODE RAY TUBE George Stanley PercivalFreeman, Chiswick, London,

England, assignor to Bush and Rank Cintel Limited,

London, England, a British company Filed Feb. 27, 1961, Ser. No. 91,825Claims priority, application Great Britain Mar. 22, 1960 6 Claims. (Cl.313-146) This invention relates to improvements in rotary screencathode-ray tubes, that is, to cathode ray tubes in which the phosphormaterial is carried upon a member arranged for rotation with respect tothe electron gun which generates the bombarding electron beam by whichthe phosphor is excited to luminescence.

A cathode ray tube of this general type which has previously beendescribed includes a phosphor-coated cylindrical anode member revolvableabout its axis which is perpendicular to and intersects that of theelectron gun. In such a tube the electron beam is scanned in onedirection only in a plane including the axes of the electron gun and ofthe anode and the remaining component of deflection for producing atwo-dimensional display is provided by the rotary movement of the anodemember.

It is a principal object of this invention to provide an improved rotaryanode cathode-ray tube.

It is a further object of this invention to provide a rotary anodecathode-ray tube with improved focusing characteristics.

It is another object of this invention to provide a tube as describedwhich has improved heat dissipating capabilities with resultant higherpower handling ability.

A still further object of this invention is to provide a rotary anodecathode-ray tube having reduced halation effects.

According to the present invention a rotary-screen cathode ray tubeincludes an electron gun for generating a beam of electrons and meansfor focusing the beam which may be deflected in a plane containing theaxis of the gun by means contained within or ancillary to the tube,together with an anode member revolvable about an axis perpendicular tothat of said gun and lying in the aforementioned plane and having aphosphor-coated surface formed by revolving, about the axis ofrevolution of the anode member, an arcuate line at least approximatelygeometrically similar to the locus of the focal point of the electronbeam in the plane of its deflection. In many cases this locus issufiiciently closely approximated by a circular are centered in saidcenter of deflection.

In an advantageous embodiment of the invention the revolvable anodemember is formed of a highly heatconductive material and contains acoaxial, cylindrical cavity within which is disposed a stationary,coolable member. This arrangement allows the peak beam current to beincreased without complex cooling arrangements.

It may also be found advantageous to apply the phosphor to the anodemember as a series of discrete, closely adjacent areas, each smallcompared with the dimensions of an elementary area of the display to bepro duced. This device improves the detail contrast available in thedisplay by preventing halation within the screen layer.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The organizationand manner of operation of the invention together with further objectsand advantages thereof, may best be understood by reference to thefollowing description taken in connection with the accompanyingdrawings, in the several figures of which like numerals identify likeelements, and in which:

FIGURE 1 is an axial cross-sectional view of one embodiment ofcathode-ray tube incorporating the present invention;

FIGURE 2 is an axial cross-sectional view of part of a preferredembodiment of cathode-ray tube according to the invention; and

FIGURE 3 is an enlarged plan view of a portion D of the luminescentscreen of the tube of FIGURE 1, modified in accordance with anotherembodiment of the invention.

The cathode-ray tube shown in FIGURE 1 comprises an evacuated glassenvelope containing an electron gun 2 arranged to generate a beam ofelectrons proceeding along the axis of symmetry of the gun, which isindicated by the broken construction line AA. The electrons are focusedby the magnetic field produced by a conventional focusing coil 3 whichis fed with direct current from a suitable source 4, and are deflectedin the plane of the paper by the magnetic field from a deflection yoke 5fed from a conventional line-scan generator 6.

The focused electron beam is thus deflected about a center of deflection(indicated by point B) along a line, lying in the plane of the drawing,on the surface of a revolvable anode 7. This anode has a surface formedby revolving about its axis a circular arc centered at center ofdeflection B. The anode conveniently comprises a phosphor-coated metalbody provided with a coaxial shaft 8 carried in bearings 9, it which areheld in protrusions 11, 12 formed in envelope 1. Shaft 8 carries therotor 13 of an induction or synchronous motor of which the stator 14 isplaced over protrusion 12 and fed with suitable currents from aconventional source (not shown).

In operation the electron beam from gun 2, modulated in the usual mannerby the signals to be displayed, is deflected by the magnetic fieldsgenerated by yoke 5 so that the point at which the electron beam assumesits narrowest cross-section is deflected about the center of deflectionB in a locus which to a first degree of approximation will be a circularare centered at the point at which the axis of gun 2 intersects theplane of symmetry of yoke 5. The true locus of the focal point of theelectron beam departs from a circle owing to the effects of the fringingfield of the yoke, but the depth of focus of the electron optical lensis often sufficient for a circular locus to be assumed.

Since the line formed by the intersection of the plane of deflectionwith the phosphor-coated surface of anode 7 is a circular arc struckfrom the center of deflection of the electron beam, the beam remainsfocused upon the screen during deflection without the usual focuscorrection. The invention is of course equally applicable to cathode-raytubes employing electrostatic deflection and focus or a combination ofelectrostatic and magnetic deflection and focus.

This construction of rotary-anode cathode ray tube possesses theadditional advantage that the optical system used to project an image ofthe display will have a curved image surface of the same general orderof curvature as the generatrix of anode 7.

FIGURE 2 shows part of a modified embodiment of the invention in whichcooling of the anode 7 is assisted by forming it with a coaxialcylindrical cavity 15 within which is disposed a cylindrical member 19closed at its inner end 20 and sealed through the wall of the envelopeby means of an integral flange 21. Conveniently there is provided withinmember 19 a pipe or conduit 22 which allows a coolant to be circulatedthrough member 19, as indicated by arrows in the figure; however this isnot essential, as cooling of member 19 may equally well be eflected byevaporation of liquid air or other volatile substance placed within it.In this case it will be necessary for the bearings, such as 9, and therotor by which anode member 7 is rotated to be placed in a singlelateral protrusion 23. It is also advantageous to blacken the internalsurface of cavity 18 and the external surface or" member 19 tofacilitate the transfer of heat by radiation.

A further improvement in the performance of such a tube may be effectedby depositing the phosphor screen on the anode member as an array ofdiscrete coated areas 25 separated from each other by uncoated areas 26,as shown in FIGURE 3. This may be done by de positing the phosphormaterial cataphoretically through a photomeehanically generated resistmask. This reduces halation due to reflection of light within thephosphor layer. The coated areas are preferably of small extent comparedwith the detail to be made visible in the display.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and, therefore the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

I claim:

1. A rotary screen cathode-ray tube comprising: an electron gun forprojecting a beam of electrons along a predetermined axis; means forfocusing said beam; means for deflecting said beam in a plane containingsaid axis; an anode member revolvable about an axis of revolutionsubstantially perpendicular to and coplanar with said predeterminedaxis; a surface of said anode member having a configurationcorresponding to that formed by revolving about said axis of revolutionan arcuate line at least approximately geometrically similar to thelocus of the focal point of said electron beam in said plane; and aphosphor coating on said surface.

2. A rotary-screen cathode ray tube according to claim 1, in which theline of intersection of the coated surface of said anode member and saidplane on the side of said axis of revolution nearer the source of saidbeam is a circular are centered at the center of deflection of saidbeam.

3. A rotary-screen cathode ray tube according to claim 2, in which saiddeflecting means are electro-magnetic deflecting means, and in whichsaid center of deflection is the point of intersection of the plane ofsymmetry of said deflecting means with the axis of said electron gun.

4. A rotary-screen cathode ray tube according to claim 1, in which saidanode member is formed of heat-conductive material and contains acoaxial, cylindrical cavity within which is disposed a stationarycoolable member.

5. A rotary-screen cathode ray tube according to claim 4, in which theinner surface of said cavity and the outer surface of said coolablemember are blackened.

6. A rotary-screen cathode ray tube according to claim 1, in which saidphosphor material is deposited on said anode member as a series ofdiscrete areas separated from each other by uncoated areas to reducehalation due to reflection of light within the phosphor deposited areas.

References Cited in the file of this patent UNITED STATES PATENTS2,086,718 Knoll July 13, 1937 2,637,827 Boyer et al. May 5, 19532,898,495 Michlin Aug. 4, 1959 2,914,696 Eshbach Nov. 24, 1959

1. A ROTARY SCREEN CATHODE-RAY TUBE COMPRISING: AN ELECTRON GUN FORPROJECTING A BEAM OF ELECTRONS ALONG A PREDETERMINED AXIS; MEANS FORFOCUSING SAID BEAM; MEANS FOR DEFLECTING SAID BEAM IN A PLANE CONTAININGSAID AXIS; AN ANODE MEMBER REVOLVABLE ABOUT AN AXIS OF REVOLUTIONSUBSTANTIALLY PERPENDICULAR TO AND COPLANAR WITH SAID PREDETERMINEDAXIS; A SURFACE OF SAID ANODE MEMBER HAVING A CONFIGURATIONCORRESPONDING TO THAT FORMED BY REVOLVING ABOUT SAID AXIS OF REVOLUTIONAN